Environment compatible image display system, image processing method and information storing medium

ABSTRACT

To provide an environment-compliant image display system, image processing method, and information storage medium that enable correction of images within a shorter time, a Y value of color signals (Y 3,  x 3,  y 3 ) measured by a color light sensor  60  and converted by an Y 3 x 3 y 3  conversion section  143  is replaced with Y 1,  which is a Y value of an ideal environment, by a Y replacing section  142;  color difference between the replaced color signals (Y 1,  x 3,  y 3 ) and ideal color signals (Y 1,  x 1,  y 1 ) is obtained by a color difference calculation section  145;  and image display information is corrected by using that color difference (Δx, Δy).

TECHNICAL FIELD

[0001] The present invention relates to an environment-compliant imagedisplay system, an image processing method, and an information storagemedium.

BACKGROUND ART

[0002] When presentations or meetings are to be performed at a pluralityof different locations, an important part of achieving an effectivepresentation is to make it possible to reproduce images exactly as thecreator of those images intended, whatever the location.

[0003] However, external light or artificial light could strike thedisplay area in which the image is displayed in practice, so there canbe a huge difference between the ideal image appearance and the actualimage appearance.

[0004] Particularly when an image is to be projected and displayed byusing a screen and projector, the image appearance can be greatlyaffected by the type of the screen.

[0005] If a screen that uses a diffused reflective plate is used, by wayof example, the reflectivity of such a screen is at least 90%, so animage thereon is seen to be much brighter than on an ordinary screenhaving a reflectivity on the order of 70%.

[0006] In addition, the distance between the screen and the projectorwill also change the image appearance.

[0007] Furthermore, it takes time to correct colors manually to ensurethat the actual image appearance is adjusted to the ideal imageappearance. For that reason if the user carries a projector to aclient's location, it takes some time to correct colors before the startof the presentation, and thus the starting time of the presentationcould be delayed for this correction.

DISCLOSURE OF INVENTION

[0008] The present invention was devised in the light of theabove-described technical problem and may provide anenvironment-compliant image display system, image processing method, andinformation storage medium that make it possible to implementsubstantially the same image appearance, within a short time.

[0009] (1) In order to solve the above described problem, an imagedisplay system of environment-compliant type which corrects imagedisplay information for displaying an image and displays the image,based on viewing environment information obtained by viewing environmentdetection means which detects a viewing environment in a display area ofthe image; the image display system comprising:

[0010] brightness correction means for correcting brightness informationincluded in the viewing environment information to conform withbrightness of an ideal environment, based on the viewing environmentinformation, when brightness of the image in the viewing environmentdiffers from brightness of the image in the ideal environment;

[0011] color difference calculation means for calculating colordifference between color information included in the viewing environmentinformation, in which the brightness information has been corrected, andcolor information of the image in the ideal environment; and

[0012] image correction means for correcting the image displayinformation, based on the calculated color difference.

[0013] (2) The present invention further relates to an image displaysystem of environment-compliant type which corrects image displayinformation for displaying an image and displays the image, based onviewing environment information obtained by viewing environmentdetection means which detects a viewing environment in a display area ofthe image; the image display system comprising:

[0014] a brightness correction section which corrects brightnessinformation included in the viewing environment information to conformwith brightness of an ideal environment, based on the viewingenvironment information, when brightness of the image in the viewingenvironment differs from brightness of the image in the idealenvironment;

[0015] a color difference calculation section which calculates colordifference between color information included in the viewing environmentinformation, in which the brightness information has been corrected, andcolor information of the image in the ideal environment; and

[0016] an image correction section which corrects the image displayinformation, based on the calculated color difference.

[0017] The present invention makes it possible to obtain a colordifference for color alone, excluding the brightness element, bycorrecting the brightness information that indicates the brightness ofthe image in the viewing environment to conform with the brightness inan ideal environment.

[0018] This makes it possible to correct image display informationrapidly, by applying the color difference as correction amount, by wayof example.

[0019] It is therefore possible to implement an image display systemthat enables corrections of the image appearance, within a short time.

[0020] Note that the brightness information may be data such as the Lvalue of colors expressed in Lab format or the Y value of colorsexpressed in Yxy format (or xyY format), by way of example. Similarly,the color information may be the a and b values of colors expressed inLab format or the x and y values of colors expressed in Yxy format.

[0021] The x value, y value, and z value in this case represent ratiosof X to Y to Z that add up to 1, and a color gamut can be expressed as abell-shaped color triangle on an xy chromaticity diagram by representingthem in Yxy format. The Lab format may also be used, enablingrepresentation of the color gamut as a circle. The Yxy format and Labformat are detected as international standards by the InternationalCommission on Illumination (CIE). The image display informationcorresponds to data such as an input-output profile or look-up table.

[0022] (3) In this image display system, the viewing environmentdetection means may measure tristimulus values of an image in thedisplay area or captures an image in the display area.

[0023] Since the measurement of the luminance of the image or thecapture of the image can be done irrespective of the distance betweenthe display means and the display area, this makes it possible to detectthe viewing environment appropriately, even if the distance between thedisplay means and the display area should change.

[0024] Note that the tristimulus values of the image may be XYZ values,RGB values, or xbar, ybar, and zbar values, or rbar, gbar, and bbarvalues which are color matching function values of those XYZ values andRGB values, by way of example.

[0025] (4) This image display system may also comprise afront-projection type image projection device including:

[0026] the brightness correction means;

[0027] the color difference calculation means;

[0028] the image correction means; and

[0029] means which projects a corrected image towards the display area.

[0030] This makes it possible to detect the viewing environmentappropriately by using the viewing environment detection means even whenusing a front-projection type image projection device (such as aprojector) and the distance between the projection means and the screenhaving a display area has been altered by a change in the environment inwhich it is installed.

[0031] (5) In this image display system, image information for the idealenvironment and the viewing environment information may be expressed inLab format or Yxy format; and

[0032] the brightness correction means may replace the L value or Yvalue of the viewing environment information with the L value or Y valueof the image information for the ideal environment.

[0033] This makes it possible to rapidly obtain a color differencebetween the color values x3 and y3 included in the viewing environmentinformation and the color values x1 and y1 for the ideal environment,when an image is expressed in Yxy format, by way of example, byreplacing the brightness value Y3 included in the viewing environmentinformation with the brightness value Y1 for the ideal environment. Notethat the image information may be an original image, by way of example.

[0034] If a projector is used to project an image on a screen, forexample, the viewing environment information will be affected by thedistance between the projector and the screen. This means that the imagewill appear darker with distance. In other words, the brightnessinformation (L value or Y value) included in the viewing environmentinformation will vary depending on the distance. The color informationin the viewing environment information will not, however, be affected bythe distance. In general, color has more effect than brightness on theimage appearance.

[0035] In other words, there is little effect on the image appearance,even when the brightness value included in the viewing environmentinformation is replaced with the brightness value for the idealenvironment. It is therefore possible to adjust the image appearance asappropriate, without having to detect the viewing environment again,even if the distance between the display area of the image (such as ascreen) and the viewing environment detection means has changed. Thismakes it possible to implement an image display system that enablescorrections of the image appearance, within a short time.

[0036] (6) The present invention still further relates to an imageprocessing method of environment-compliant type which corrects imagedisplay information for displaying an image, based on viewingenvironment information indicating a viewing environment in a displayarea of the image, the image processing method comprising:

[0037] a step of generating the viewing environment information;

[0038] a color difference detection step of detecting color differencebetween a given image in the viewing environment and the given image inan ideal environment, based on the generated viewing environmentinformation; and

[0039] a step of correcting the image display information, based on thedetected color difference.

[0040] The present invention makes it possible to correct image displayinformation rapidly, by applying color difference as correction amount,by way of example.

[0041] It is therefore possible to correct the image appearance, withina short period of time.

[0042] (7) In this image processing method, the viewing environmentinformation may comprise color information indicating color of the imagein the viewing environment and brightness information indicatingbrightness of the image in the viewing environment; and

[0043] the color difference detection step may comprise:

[0044] a brightness correction step which corrects brightnessinformation included in the viewing environment information to conformwith brightness of the ideal environment, based on the viewingenvironment information, when brightness of the image in the viewingenvironment differs from brightness of the image in the idealenvironment; and

[0045] a step of calculating the color difference based on colorinformation included in the viewing environment information, in whichthe brightness information has been corrected, and color information ofthe image in the ideal environment.

[0046] This makes it possible to obtain color difference for coloralone, excluding the brightness element, by correcting the brightnessinformation that indicates the brightness of the image in the viewingenvironment to conform with the brightness in an ideal environment.

[0047] The correction of color of the image can be done more rapidly byusing color difference that takes only colors into account.

[0048] (8) In this image processing method, image information for theideal environment and the viewing environment information may beexpressed in Lab format or Yxy format; and

[0049] the brightness correction step may comprise a step of replacingthe L value or Y value of the viewing environment information with the Lvalue or Y value of the image information for the ideal environment.

[0050] This makes it possible to rapidly obtain the color values x3 andy3 included in the viewing environment information and the color valuesx1 and y1 for the ideal environment, when an image is expressed in Yxyformat, byway of example, by replacing the brightness value Y3 includedin the viewing environment information with the brightness value Y1 forthe ideal environment.

[0051] (9) The present invention yet further relates to acomputer-readable information storage medium which stores program forcorrecting image display information for displaying an image, based onviewing environment information indicating a viewing environment in adisplay area of the image, the information storage medium comprisingprogram to implement on a computer:

[0052] means which generates the viewing environment information;

[0053] color difference detection means which detects color differencebetween a given image in the viewing environment and the given image inan ideal environment, based on the generated viewing environmentinformation; and

[0054] means which corrects the image display information, based on thedetected color difference.

[0055] The present invention makes it possible to correct image displayinformation rapidly, by applying color difference as correction amount,by way of example.

[0056] It is therefore possible to correct the image appearance, withina short period of time.

[0057] (10) In this information storage medium, the viewing environmentinformation may comprise color information indicating color of the imagein the viewing environment and brightness information indicatingbrightness of the image in the viewing environment; and

[0058] the color difference detection means may comprise:

[0059] brightness correction means which corrects brightness informationincluded in the viewing environment information to conform withbrightness in the ideal environment, based on the viewing environmentinformation, when brightness of the image in the viewing environmentdiffers from brightness of the image in the ideal environment; and

[0060] means which calculates the color difference based on colorinformation included in the viewing environment information, in whichthe brightness information has been corrected, and color information ofthe image in the ideal environment.

[0061] This makes it possible to obtain color difference for coloralone, excluding the brightness element, by correcting the brightnessinformation that indicates the brightness of the image in the viewingenvironment to conform with the brightness in an ideal environment.

[0062] The correction of color of the image can be done more rapidly byusing color difference that takes only colors into account. (11) In thiainformation storage medium, image information for the ideal environmentand the viewing environment information may be expressed in Lab formator Yxy format; and

[0063] the brightness correction means may replace the L value or Yvalue of the viewing environment information with the L value or Y valueof the image information for the ideal environment.

[0064] This makes it possible to rapidly obtain the color values x3 andy3 included in the viewing environment information and the color valuesx1 and y1 for the ideal environment, when an image is expressed in Yxyformat, byway of example, by replacing the brightness value Y3 includedin the viewing environment information with the brightness value Y1 forthe ideal environment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0065]FIG. 1 is a schematic illustrative view of an image display systemin accordance with an example of this embodiment;

[0066]FIG. 2 is a functional block diagram of an image processingsection within a conventional projector;

[0067]FIG. 3 is a functional block diagram of the image processingsection within a projector in accordance with an example of thisembodiment;

[0068]FIG. 4 is a functional block diagram of the color light sensor inaccordance with an example of this embodiment;

[0069]FIG. 5 is a graph of color matching functions;

[0070]FIG. 6 is a functional block diagram of the color lightinformation processing section in accordance with an example of thisembodiment; and

[0071]FIG. 7 is a schematic view of color conversion in an xychromaticity diagram.

BEST MODE FOR CARRYING OUT THE INVENTION

[0072] The description below relates to a case in which the presentinvention is applied to an image display system which uses aliquid-crystal projector, with reference to the accompanying figures.Note that the embodiments described herein do not in any way limit thescope of the invention as defined by the claims. Similarly, the entiretyof the configuration described for these embodiments does not place anylimitations on the essential components of the means in accordance withthe present invention, as laid out herein.

[0073] Description of overall System

[0074] A schematic illustrative view of an image display system inaccordance with an example of this embodiment of the present inventionis shown in FIG. 1.

[0075] A projector 20, which is a front-projection type display deviceprovided substantially facing a screen 10, projects an image for apredetermined presentation. A presenter 30 gives a presentation to anaudience, while using a light spot 70 projected from a laser pointer 50to point at a desired position of an image in an image display region12, which is a display area on the screen 10.

[0076] During such a presentation, the image appearance on the imagedisplay region 12 will vary greatly, depending on factors such as thetype of the screen 10 and ambient light 80. When the projector 20displays the same white, for example, the type of the screen 10 couldmake it seem to be white with a yellow cast or white with a blue cast.Similarly, differences in the ambient light 80 could make the same whitethat is displayed by the projector 20 appear to be a bright white or adull white.

[0077] In recent years, this projector 20 has become smaller and easierto transport. For that reason, it has become possible for the presenter30 to perform presentations at a client's location, byway of example,but it is difficult to adjust colors to match the environment at theclient's location and the manual adjustment of colors at the client'slocation takes too much time.

[0078] A functional block diagram of the image processing section withina conventional projector is shown in FIG. 2.

[0079] This conventional projector inputs an R1 signal, a G1 signal, anda B1 signal (which form RGB signals in analog format, sent from a PC orthe like) to an A/D converter section 110, and uses a projector imageprocessing section 100 to perform color conversion on an R2 signal, a G2signal, and a B2 signal that have been converted into digital form bythe A/D converter section 110.

[0080] An R3 signal, a G3 signal, and a B3 signal that have beensubjected to the color conversion are input to a D/A converter section180, and an R4 signal, a G4 signal, and a B4 signal that have beenconverted into analog form are input to a light valve (L/V) drivesection 190, to drive a liquid-crystal light valve and thereby displayan image.

[0081] The projector image processing section 100, which is controlledby a CPU 200 comprises a projector color conversion section 120 and aprofile management section 130.

[0082] The projector color conversion section 120 converts the RGBdigital signals (the R2 signal, G2 signal, and B2 signal) from the A/Dconverter section 110 into RGB digital signals for projector output (theR3 signal, G3 signal, and B3 signal), based on a projector input-outputprofiles that are managed by the profile management section 130. Notethat “profile” in this case refers to characteristic data.

[0083] In this manner, the conventional projector can only perform colorconversion based on input-output profiles that indicate input-outputcharacteristics which are specific to that particular projector, andthus no consideration is paid to the viewing environment in which theimage is projected and displayed.

[0084] However, it is difficult to ensure that the color appearance isuniform with this configuration, without taking the viewing environmentinto account. The color appearance is detected by three factors: light,the reflection or transmission of light by objects, and vision.

[0085] This embodiment of the present invention implements an imagedisplay system that can reproduce identical colors, by detecting theviewing environment of light as well as the reflection or transmissionof that light by objects, irrespective of the environment in which it isused.

[0086] The image appearance is also affected by the distance between theprojector 20 and the screen 10. It is possible to measure the distancebetween the projector 20 and the screen 10 and correct the image fromconsideration of that distance, but the provision of a distancemeasurement means in addition to the image correction means would makethe image display system itself much larger.

[0087] With this embodiment, images are corrected without having toprovide a distance measurement means, by applying an image processingmethod that is not dependent on the distance between the projector 20and the screen 10.

[0088] More specifically, the device is provided with a color lightsensor 60 that functions as viewing environment detection means fordetecting the viewing environment, as shown in FIG. 1, where viewingenvironment information from the color light sensor 60 is input to theprojector 20. The color light sensor 60 measures viewing environmentinformation (more specifically, RGB or XYZ tristimulus values) withinthe image display region 12 of the screen 10.

[0089] The projector 20 is provided with brightness correction means,for correcting brightness information that is included in the viewingenvironment information to conform with the brightness of the idealenvironment, based on the viewing environment information, if the imagebrightness in the viewing environment differs from the image brightnessin the ideal environment; color difference calculation means forcalculating color difference between color information included in theviewing environment information, in which the brightness information hasbeen corrected and color information of an image in the idealenvironment; and image correction means for correcting image displayinformation that is used for displaying the image, based on thethus-calculated color difference.

[0090] The use of this configuration enables the implementation of animage display system that corrects images, irrespective of the distancebetween the projector 20 and the screen 10.

[0091] Note that the sequence of image processing for correcting theimage is such that a white image is projected from the projector 20 tothe screen 10 at each of predetermined gray scales and the viewingenvironment is detected by measuring tristimulus values of the image inthe image display region 12 by the color light sensor 60.

[0092] The correction of the image display information for each of thosegray scales is based on those tristimulus values.

[0093] The description now turns to details of the image processingmethod performed to correct the image, using the functional blocks ofthe image processing section of the projector 20 which comprisescomponents such as the above brightness correction means.

[0094] A functional block diagram of the image processing section withinthe projector 20 in accordance with an example of this embodiment isshown in FIG. 3.

[0095] The projector 20 inputs the R1 signal, G1 signal, and B1 signal(which form RGB signals in analog format, sent from a PC or the like) tothe A/D converter section 110, and the projector image processingsection 100 performs color conversion on the digital R2 signal, G2signal, and B2 signal.

[0096] The projector 20 inputs the color-converted R3 signal, G3 signal,and B3 signal to the D/A converter section 180, then inputs theanalog-converted R4 signal, G4 signal, and B4 signal to the light valve(L/V) drive section 190 which projects and displays an image by drivingliquid-crystal light valves.

[0097] Up until this point, there is no difference from theconfiguration of the conventional projector. The projector imageprocessing section 100 of the projector 20 in accordance with thisembodiment comprises a color signal conversion section 160, a colorsignal reverse-conversion section 170, a color management section 150,and the projector color conversion section 120.

[0098] The color signal conversion section 160 converts the digital RGBsignals (R2 signal, G2 signal, and B2 signal) from the A/D convertersection 110 into XYZ values (X1, Y1, Z1). Note that the colorsrepresented by RGB signals are device-dependent colors that are affectedby the input-output device, such as the projector 20, whereas the colorsrepresented by the XYZ values are device-independent colors that are thesame regardless of the device.

[0099] Note also that a method such as a matrix-conversion method usinga 3×3 matrix can be used as the specific method for converting from theRGB digital signals to the XYZ values.

[0100] The color signal conversion section 160 outputs thethus-converted XYZ values (X1, Y1, Z1) to the color management section150.

[0101] The color management section 150 converts the XYZ values (X1, Y1,Z1), which that have been input from the color signal conversion section160, into XYZ values (X2, Y2, Z2) that take into account the viewingenvironment, based on a measured value from the color light sensor 60that is the viewing environment detection means.

[0102] The description now turns to details of the color light sensor60.

[0103] A functional block diagram of the color light sensor 60 inaccordance with an example of this embodiment is shown in FIG. 4. Agraph of color matching functions is shown in FIG. 5.

[0104] The color light sensor 60 comprises an xbar input section 61, aybar input section 62, and a zbar input section 63 that input thecorresponding tristimulus values xbar, ybar, and zbar, of the colormatching functions in the XYZ color system, as shown in FIG. 5.

[0105] The color light sensor 60 also comprises an XYZ conversionsection 64 that converts the xbar, ybar, and zbar values, which areinput from the xbar input section 61, the ybar input section 62, and thezbar input section 63, into X3, Y3, and Z3 values.

[0106] Note that a known conversion formula could be used for convertingthe xbar value and the like into the X3 value and the like, with theconversion formula being discussed, for example, in Handbook of ColorScience (second edition), published by University of Tokyo Press.

[0107] The color management section 150 also comprises a color lightinformation processing section 140 and the profile management section130 that manages the above described input-output profiles for theprojector 20.

[0108] The description now turns to details of the color lightinformation processing section 140.

[0109] A functional block diagram of the color light informationprocessing section 140 in accordance with an example of this embodimentis shown in FIG. 6.

[0110] The color light information processing section 140 comprises aY1x1y1 conversion section 141, which converts color signals (X1, Y1, Z1)in XYZ format for an ideal environment from the color signal conversionsection 160 into color signals (Y1, x1, y1) in Yxy format; a Y3x3y3conversion section 143, which converts color signals (X3, Y3, Z3) in XYZformat from the color light sensor 60 that represent the viewingenvironment into color signals (Y3, x3, y3) in Yxy format; and a Yreplacing section 142 that functions as brightness correction means.

[0111] The Y replacing section 142 replaces Y3 of the color signals (y3,x3, y3) with Y1, based on Y1, which is part of the color signals fromthe color signal conversion section 160, and the color signals (Y3, x3,y3) from the Y3x3y3 conversion section 143.

[0112] This makes it possible to calculate the color difference in astate in which the brightness of the color information for the idealenvironment and the color information in the actual viewing environmentis completed, during processing by the Y replacing section 142 andsubsequent components, by converting the brightness information Y3included in the environment information for the viewing environment intoY1 in such a manner that it conforms with the brightness in the idealenvironment. This makes it possible to perform the calculations at ahigher speed, because only the color difference for the color alone needbe calculated.

[0113] The color light information processing section 140 comprises acolor difference correction calculation section 144 that calculatescolor difference and a tristimulus values conversion section 147 thatconverts color signals into tristimulus values (X2, Y2, Z2), based onthe thus-calculated color difference.

[0114] The color difference correction calculation section 144 comprisesa color difference calculation section 145 and a Y2x2y2 conversionsection 146.

[0115] The color difference calculation section 145 calculates colordifference between the color signals (Y1, x3, y3) from the Y replacingsection 142 and the color signals (Y1, x1, y1) from the Y1x1y1conversion section 141.

[0116] Since the Y1 values (indicating brightness) of these two sets ofcolor signals match, the color difference between the values (x3, y3)and (x1, y1) expressed on an xy chromaticity diagram can be calculated.

[0117] As a result, the color difference Ax between x3 and x1 and thecolor difference Δy between y3 and y1 are obtained.

[0118] A schematic view of the color conversion in an xy chromaticitydiagram is shown in FIG. 7.

[0119] If it is assumed, by way of example, that a point P (x3, y3)indicates the color of an image in the actual viewing environment and apoint I (x1, y1) indicates the color of the image in an idealenvironment, the color shift from the ideal color can be expressed by Δxand Δy, as shown in FIG. 7.

[0120] To correct this shift, this Δx and Δy could be used as correctionamounts for correcting the color of the image.

[0121] The point indicating the color after the correction is denoted bya point P′ (x2, y2). In other words, it becomes possible to reproducethe ideal color of the point I (x1, y1) in the actual viewingenvironment, which has been affected by factors such as ambient light,by outputting the color of the point P′ (x2, y2).

[0122] The Y2x2y2 conversion section 146 outputs values (x2, y2), whichare obtained by correcting the ideal color (x1, y1) using Δx and Δy ascorrection amounts, together with Y2 to the tristimulus valuesconversion section 147. Note that the tristimulus values conversionsection 147 uses Y1 as Y2 without modification.

[0123] The tristimulus values conversion section 147 converts the colorsignals (Y2, x2, y2) from the Y2x2y2 conversion section 146 intotristimulus values (X2, Y2, Z2).

[0124] The color light information processing section 140 outputs thetristimulus values (X2, Y2, Z2) from the tristimulus values conversionsection 147 to the color signal reverse-conversion section 170.

[0125] The profile management section 130 functions as the abovedescribed image correction means and creates the input-output profilesfor the RGB signals of the projector 20. Note that each input-outputprofile is part of the information for image display used for displayingimages. The profile management section 130 also manages the RGBinput-output characteristics of the projector 20, using the thus-createdinput-output profiles for the RGB signals.

[0126] The color signal reverse-conversion section 170 performs areverse conversion on the XYZ values (X2, Y2, Z2) from the color lightinformation processing section 140 to convert them into RGB digitalsignals (an R5 signal, a G5 signal, and a B5 signal), using a inversematrix of the above-described matrix of the color signal conversionsection 160.

[0127] The projector color conversion section 120 converts the RGBdigital signals (the R5 signal, G5 signal, and B5 signal) from the colorsignal reverse-conversion section 170 into the RGB digital signals (theR3 signal, G3 signal, and B3 signal) for projector output, withreference to projector profiles managed by the profile managementsection 130.

[0128] The projector image processing section 100 that is controlled bythe CPU 200 comprises the projector color conversion section 120 and theprofile management section 130.

[0129] The projector color conversion section 120 converts the RGBdigital signals (the R6 signal, G6 signal, and B6 signal) from the A/Dconverter section 110 into the RGB digital signals for projector output(the R3 signal, G3 signal, and B3 signal), based on the input-outputprofiles for the RGB signals that are managed by the profile managementsection 130.

[0130] The RGB digital signal for projector output that have been outputfrom the projector color conversion section 120 are converted into theRGB analog signals (the R4 signal, G4 signal, and B4 signal) by the D/Aconverter section 180, and liquid-crystal light valves are driven by theL/V drive section 190 to project and display an image, based on thoseRGB analog signals.

[0131] As described above, a presentation image that has been correctedin a manner that is appropriated for the viewing environment can bedisplayed, when image display information is corrected for each grayscales and the actual presentation image is displayed.

[0132] Thus images are projected and displayed in this embodiment,taking the viewing environment into account.

[0133] This makes it possible to display an image that conforms with theviewing environment during image display, so that differences in displayenvironment can be absorbed and the same image can be displayedirrespective of the environment that is applied. It is thereforepossible to reproduce substantially the same colors within a shortperiod of time, at a plurality of different locations.

[0134] This embodiment makes it possible to obtain color difference forcolor alone, excluding the brightness element, by correcting thebrightness information that indicates the brightness of the image in theviewing environment to conform with the brightness in an idealenvironment.

[0135] In particular, it is possible to rapidly obtain the colordifference between color values x3 and y3 included in the viewingenvironment information and the color values x1 and y1 in the idealenvironment, by replacing the brightness value Y3 included in theviewing environment information with the brightness value Y1 for theideal environment.

[0136] If the projector 20 is used to project an image on the screen 10,as in this embodiment, the viewing environment information will beaffected by the distance between the projector 20 and the screen 10.This means that the image will appear darker with distance. In otherwords, the brightness information (L value or Y value) included in theviewing environment information will vary with this distance. The colorinformation within the viewing environment information will not,however, be affected by distance. In general, color has more effect thanbrightness on the image appearance.

[0137] In other words, there is little effect on the image appearance,even when the brightness value Y3 included in the viewing environmentinformation is replaced with the brightness value Y1 for the idealenvironment, as in this embodiment. It is therefore possible to adjustthe image appearance as appropriate, without having to detect theviewing environment again, even if the distance between the display areafor the image (such as the screen) and the viewing environment detectionmeans has changed.

[0138] Since the image display information can be corrected rapidlyirrespective of the distance between the color light sensor 60 and theimage display region 12, as described above, it is possible to implementa system that ensures that the image appearance is substantially thesame at a plurality of different locations, within a short period oftime.

[0139] Description of Hardware

[0140] Note that the hardware described below by way of example can beused to implement the above described components.

[0141] For example, the configuration could be implemented by an A/Dconverter or the like as the A/D converter section 110; a D/A converteror the like as the D/A converter section 180; a liquid-crystal lightvalve driver as the L/V drive section 406; an image processing circuitand ASIC or the like as the projector color conversion section 120, thecolor signal conversion section 160, the color signal reverse-conversionsection 170, and the color light information processing section 140; andcircuitry having a storage area such as RAM or the like as the profilemanagement section 130. Note that these components could be implementedin a hardware fashion by circuitry, or they could be implemented in asoftware fashion by drivers.

[0142] In addition, the functions of the components could be implementedby reading out a program from an information storage medium 300, asshown in FIG. 3. The information storage medium 300 could be a CD-ROM,DVD-ROM, ROM. RAM, or HDD, by way of example, and the method of readingthe program therefrom could be a direct method or an indirect method.

[0143] Instead of the information storage medium 300, it is possible toimplement the above described functions by downloading a program or thelike that implements those functions over a transmission path from ahost device or the like. In other words, a program for implementingthese functions could be embodied over carrier waves.

[0144] The hardware described below may be employed for the color lightsensor 60.

[0145] The xbar input section 61, the ybar input section 62, and thezbar input section 63 may each be, for example, a color filter andphotodiode that are selectively transparent with respect to thecorresponding stimulus value, and the XYZ conversion section 64 may be,for example, an A/D converter that converts an analog signal from thephotodiode into a digital signal and an op-amp that amplifies thatdigital signal.

[0146] Note the present invention has been described above by way of oneembodiment thereof, but the application of the present invention is notlimited to the above embodying example.

[0147] Modification

[0148] For example, the tristimulus values that are input by the colorlight sensor 60 are not limited to xbar, ybar, and zbar values; they mayequally well be XYZ values, RGB values, or rbar, gbar and bbar valuesthat are color matching function values of RGB values, by way ofexample.

[0149] In addition, the viewing environment detection means may beimaging means such as a CCD camera or a CMOS camera, instead of thecolor light sensor 60.

[0150] Furthermore, the description of the embodying example aboverelates to an example of the correction of an image by the Yxy format,but it is equally possible to perform image correction by another typeof representative format having brightness information and colorinformation, such as the Lab format or Luv format. If the Lab format isused, by way of example, it is possible to correct the image by a methodsimilar to the above described one, by reading Y as L and x and y as aand b.

[0151] Note that the above described screen 10 is of a reflective typebut it may equally well be of a transparent type.

[0152] The present invention may also be applied to presentations inwhich images are displayed by a display means other than a projectionmeans such as the above described projector. Apart from a liquid-crystalprojector, this display means may be a cathode ray tube (CRT), a plasmadisplay panel (PDP), a field emission display (FED), anelectro-luminescence (EL) device, or a direct-view type liquid crystaldisplay device, or a projector using a digital micromirror device (DMD).by way of example. Note that DMD is a tradename registered by TexasInstruments Inc., of the US. In addition, the projector is not limitedto a front-projection type device; it may equally well be of arear-projection type.

[0153] The time required for image correction may be shortened by theabove described method of replacing brightness information, even whenthe present invention is applied to the above types of image displaymeans.

[0154] Note that it is possible to correct the image irrespective ofdistance, even when the present invention is applied to image displaymeans in which the distance between the projected position of the imageand the display area of the image varies, as in a front-projection typeprojector.

[0155] In addition to presentations, this invention is also effective inthe display of images such as those at meetings, during medicaltreatment, in the design and fashion fields, business activities,commercials, and education, as well as general-purpose images such asthose in movies, TV, videos, and games.

[0156] Note that the functions of the above-described projector imageprocessing section 100 of the projector 20 could be implemented by asingle image display device (such as the projector 20 itself) or bydistribution between a plurality of processing devices (such asdistributed processing between the projector 20 and a PC).

1. An image display system of environment-compliant type which correctsimage display information for displaying an image and displays theimage, based on viewing environment information obtained by viewingenvironment detection means which detects a viewing environment in adisplay area of the image; the image display system comprising:brightness correction means for correcting brightness informationincluded in the viewing environment information to conform withbrightness of an ideal environment, based on the viewing environmentinformation, when brightness of the image in the viewing environmentdiffers from brightness of the image in the ideal environment; colordifference calculation means for calculating color difference betweencolor information included in the viewing environment information, inwhich the brightness information has been corrected, and colorinformation of the image in the ideal environment; and image correctionmeans for correcting the image display information, based on thecalculated color difference.
 2. The image display system as defined inclaim 1, wherein the viewing environment detection means measurestristimulus values of an image in the display area or captures an imagein the display area.
 3. The image display system as defined in claim 2,comprising a front-projection type image projection device including:the brightness correction means; the color difference calculation means;the image correction means; and means which projects a corrected imagetowards the display area.
 4. The image display system as defined inclaim 3, wherein image information for the ideal environment and theviewing environment information are expressed in Lab format or Yxyformat; and wherein the brightness correction means replaces the L valueor Y value of the viewing environment information with the L value or Yvalue of the image information for the ideal environment.
 5. An imagedisplay system of environment-compliant type which corrects imagedisplay information for displaying an image and displays the image,based on viewing environment information obtained by viewing environmentdetection means which detects a viewing environment in a display area ofthe image; the image display system comprising: a brightness correctionsection which corrects brightness information included in the viewingenvironment information to conform with brightness of an idealenvironment, based on the viewing environment information, whenbrightness of the image in the viewing environment differs frombrightness of the image in the ideal environment; a color differencecalculation section which calculates color difference between colorinformation included in the viewing environment information, in whichthe brightness information has been corrected, and color information ofthe image in the ideal environment; and an image correction sectionwhich corrects the image display information, based on the calculatedcolor difference.
 6. An image processing method of environment-complianttype which corrects image display information for displaying an image,based on viewing environment information indicating a viewingenvironment in a display area of the image, the image processing methodcomprising: a step of generating the viewing environment information; acolor difference detection step of detecting color difference between agiven image in the viewing environment and the given image in an idealenvironment, based on the generated viewing environment information; anda step of correcting the image display information, based on thedetected color difference.
 7. The image processing method as defined inclaim 6, wherein the viewing environment information comprises colorinformation indicating color of the image in the viewing environment andbrightness information indicating brightness of the image in the viewingenvironment; and wherein the color difference detection step comprises:a brightness correction step which corrects brightness informationincluded in the viewing environment information to conform withbrightness of the ideal environment, based on the viewing environmentinformation, when brightness of the image in the viewing environmentdiffers from brightness of the image in the ideal environment; and astep of calculating the color difference based on color informationincluded in the viewing environment information, in which the brightnessinformation has been corrected, and color information of the image inthe ideal environment.
 8. The image processing method as defined inclaim 7, wherein image information for the ideal environment and theviewing environment information are expressed in Lab format or Yxyformat; and wherein the brightness correction step comprises a Step ofreplacing the L value or Y value of the viewing environment informationwith the L value or Y value of the image information for the idealenvironment.
 9. A computer-readable information storage medium whichstores program for correcting image display information for displayingan image, based on viewing environment information indicating a viewingenvironment in a display area of the image, the information storagemedium comprising program to implement on a computer: means whichgenerates the viewing environment information; color differencedetection means which detects color difference between a given image inthe viewing environment and the given image in an ideal environment,based on the generated viewing environment information; and means whichcorrects the image display information, based on the detected colordifference.
 10. The information storage medium as defined in claim 9,wherein the viewing environment information comprises color informationindicating color of the image in the viewing environment and brightnessinformation indicating brightness of the image in the viewingenvironment; and wherein the color difference detection means comprises:brightness correction means which corrects brightness informationincluded in the viewing environment information to conform withbrightness in the ideal environment, based on the viewing environmentinformation, when brightness of the image in the viewing environmentdiffers from brightness of the image in the ideal environment; and meanswhich calculates the color difference based on color informationincluded in the viewing environment information, in which the brightnessinformation has been corrected, and color information of the image inthe ideal environment.
 11. The information storage medium as defined inclaim 10, wherein image information for the ideal environment and theviewing environment information are expressed in Lab format or Yxyformat; and wherein the brightness correction means replaces the L valueor Y value of the viewing environment information with the L value or Yvalue of the image information for the ideal environment.